A PACAC report said that the EU referendum website crash may have been caused by a DDoS attack.

Foreign governments may have interfered with the Brexit vote, according to a committee of MPs. Concerns have reportedly been raised over allegations that foreign governments such as Russia and China may have been involved in tampering an EU referendum voter website, that crashed on 7 June, 100 minutes before the deadline, forcing ministers to extend the deadline to register.

According to a report by the Commons public administration and constitutional affairs committee (PACAC), MPs have raised concerns about allegations of interference in 2016's Brexit vote by foreign states. The report failed to identify parties that may have been responsible. However, the committee noted that Russia and China have been known to use such cyberattacks, based on their understanding of how to manipulate voters.

The report, published on Wednesday (12 April), said that there is evidence to suggest that a DDoS attack, leveraging a botnet, may have been used to overwhelm the site and bring it down. "The crash had indications of being a DDOS 'attack'. We understand that this is very common and easy to do with botnets... The key indicants are timing and relative volume rate," the committee's report said.

The committee also said that despite the fact that the incident has no bearing on the outcome of the vote, it is essential that the government improve its cybersecurity to better safeguard future votes.

The report noted: "The US and UK understanding of 'cyber' is predominantly technical and computer network-based.

"For example, Russia and China use a cognitive approach based on understanding of mass psychology and of how to exploit individuals. The implications of this different understanding of cyber-attack, as purely technical or as reaching beyond the digital to influence public opinion, for the interference in elections and referendums are clear.

"PACAC is deeply concerned about these allegations about foreign interference," the report concluded.

GCHQ's new security head Ciaran Martin previously said that Britain was the target of numerous attacks every month, which include attempts by Russian state-sponsored hackers to steal defence and state secrets. In February, UK's National Cyber Security Centre (NCSC) finally opened its doors as fears of Russia's alleged aggression in cyberspace mounted.